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The following table identifies a group of children by one of four hair colors, and by type of hair.

Hair Type Brown Blond Black Red Totals
Wavy 20 15 3 43
Straight 80 15 12
Totals 20 215
  • Complete the table above.
  • What is the probability that a randomly selected child will have wavy hair?
  • What is the probability that a randomly selected child will have either brown or blond hair?
  • What is the probability that a randomly selected child will have wavy brown hair?
  • What is the probability that a randomly selected child will have red hair, given that he has straight hair?
  • If B is the event of a child having brown hair, find the probability of the complement of B.
  • In words, what does the complement of B represent?
  • 43 215
  • 120 215 size 12{ { { size 8{"120"} } over { size 8{"215"} } } } {}
  • 20 215
  • 12 172
  • 115 215 size 12{ { { size 8{"115"} } over { size 8{"215"} } } } {}

A previous year, the weights of the members of the San Francisco 49ers and the Dallas Cowboys were published in the San Jose Mercury News . The factual data are compiled into the following table.

Shirt# ≤ 210 211-250 251-290 290≤
1-33 21 5 0 0
34-66 6 18 7 4
66-99 6 12 22 5

For the following, suppose that you randomly select one player from the 49ers or Cowboys.

  • Find the probability that his shirt number is from 1 to 33.
  • Find the probability that he weighs at most 210 pounds.
  • Find the probability that his shirt number is from 1 to 33 AND he weighs at most 210 pounds.
  • Find the probability that his shirt number is from 1 to 33 OR he weighs at most 210 pounds.
  • Find the probability that his shirt number is from 1 to 33 GIVEN that he weighs at most 210 pounds.
  • If having a shirt number from 1 to 33 and weighing at most 210 pounds were independent events, then what should be true about P(Shirt# 1-33 | ≤ 210 pounds) ?

Approximately 281,000,000 people over age 5 live in the United States. Of these people, 55,000,000 speak a language other than English at home. Of those who speak another language at home, 62.3% speak Spanish. ( Source: http://www.census.gov/hhes/socdemo/language/data/acs/ACS-12.pdf )

Let: E = speak English at home; E' = speak another language at home; S = speak Spanish;

Finish each probability statement by matching the correct answer.

Probability Statements Answers
a. P(E') = i. 0.8043
b. P(E) = ii. 0.623
c. P(S and E') = iii. 0.1957
d. P(S|E') = iv. 0.1219

  • iii
  • i
  • iv
  • ii

The probability that a male develops some form of cancer in his lifetime is 0.4567 (Source: American Cancer Society). The probability that a male has at least one false positive test result (meaning the test comes back for cancer when the man does not have it) is 0.51 (Source: USA Today). Some of the questions below do not have enough information for you to answer them. Write “not enough information” for those answers.

Let: C = a man develops cancer in his lifetime; P = man has at least one false positive

  • Construct a tree diagram of the situation.
  • P(C) =
  • P (P|C) =
  • P (P|C' ) =
  • If a test comes up positive, based upon numerical values, can you assume that man has cancer? Justify numerically and explain why or why not.

In 1994, the U.S. government held a lottery to issue 55,000 Green Cards (permits for non-citizens to work legally in the U.S.). Renate Deutsch, from Germany, was one of approximately 6.5 million people who entered this lottery. Let G = won Green Card .

  • What was Renate’s chance of winning a Green Card? Write your answer as a probability statement.
  • In the summer of 1994, Renate received a letter stating she was one of 110,000 finalists chosen. Once the finalists were chosen, assuming that each finalist had an equal chance to win, what was Renate’s chance of winning a Green Card? Let F = was a finalist . Write your answer as a conditional probability statement.
  • Are G and F independent or dependent events? Justify your answer numerically and also explain why.
  • Are G and F mutually exclusive events? Justify your answer numerically and also explain why.
P.S. Amazingly, on 2/1/95, Renate learned that she would receive her Green Card -- true story!

  • P ( G ) = 0 . 008 size 12{P \( G \) =0 "." "008"} {}
  • 0.5
  • dependent
  • No

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Source:  OpenStax, Collaborative statistics for mt230. OpenStax CNX. Aug 18, 2011 Download for free at http://legacy.cnx.org/content/col11345/1.2
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